Rroblem with Style/HashSyntax cop in Ruby 3.1

[tycooon]

When using ruby 3.1 hash syntax, I get the Lint/UselessAssignment cop warning.

Expected behavior

No warnings.

Actual behavior

1.rb:4:3: W: Lint/UselessAssignment: Useless assignment to variable - user.
  user = double :user, id: 42, token:
  ^^^^

1 file inspected, 1 offense detected

Steps to reproduce the problem

def some_method(token)
  user = double :user, id: 42, token:
  described_class.build(user)
end

Version with brackets works as expected:

def some_method(token)
  user = double(:user, id: 42, token:)
  described_class.build(user)
end

RuboCop version

1.24.1 (using Parser 3.1.0.0, rubocop-ast 1.15.1, running on ruby 3.1.0 arm64-darwin21)

Update:

It turns out that Ruby interprets the first one as

  user = double :user, id: 42, token: described_class.build(nil)

So technically this is not a false positive. However, this also means that auto-correction for Style/HashSyntax cop is not safe in this case. So probably this should be fixed somehow.

[koic]

In Ruby 3.1, the following code is equivalent. So, line breaked expression is the hash value.

def some_method(token)
  user = double :user, id: 42, token:
  described_class.build(user)
end

def some_method(token)
  user = double :user, id: 42, token: described_class.build(user)
end

This behavior is being considered in the following Ruby core issue.
https://bugs.ruby-lang.org/issues/18396

So technically this is not a false positive. However, this also means that auto-correction for Style/HashSyntax cop is not safe in this case. So probably this should be fixed somehow.

This issue has been resolved by #10357. It will be included in the next release.

[tycooon]

I tested with version 1.25.0 and it looks like it still breaks the code with auto-correction even in safe mode. For example, it replaces

build :user, token: token
SomeClass.new(true) 

with

build :user, token:
SomeClass.new(true)

Which breaks the code. Note that if there is SomeClass.new without an argument, it doesn't report a warning.

Also, now it doesn't do auto-correction in a lot of safe cases even with EnforcedShorthandSyntax: always option. So I guess some more fixes are needed.

[tycooon]

Example when 1.25 doesn't report a warning where 1.24 did:

p Hash[x: x]

and

def attrs(user, token)
  {
    user: user,
    token: token
  }
end

[koic]

@tycooon Your feedback is correct. I've opened #10363 to resolve the issues. Thank you!

[tycooon]

Great, thank you 👍